INACTIVATION OF PANCREATIC AND GASTRIC LIPASES BY THL AND C-12-0-TNB - A KINETIC-STUDY WITH EMULSIFIED TRIBUTYRIN

THL is a potent inhibitor of pancreatic (PPL) and gastric (HGL, RGL) lipases. Inactivation occurs preferentially at the oil/water interface (method B, C). In the aqueous phase (method A), the inhibition of HGL was accelerated by the presence of bile salts. C12:0-TNB, a disulfide reagent, specifically inactivates gastric lipases and had no effect on the pancreatic lipase (in the presence of bile salts) whatever the method used. The capacity of THL and C12:0-TNB to inactivate lipases using Methods B and C was found to depend directly upon the interfacial area of the system used. Consequently, inactivation can be reduced or prevented by further addition of a water-insoluble substrate which reduces the surface density of inactivator molecules. With a heterogeneous system of this kind, typical of lipolysis, the use of a classical Michaelis-Menten model is irrelevant and hence the traditional kinetic parameters (K(m), K(I), V(max)) are only apparent values.